Sylvia Koge a medical technologist holds a sample to be used in a rapid flu test at Methodist Emergency Care Center-Kirby, 2615 SW Freeway, Tuesday, Jan. 8, 2013, in Houston. By December, Texas was among five states with high levels of flu. That uptick continued into the last week of 2012 when an estimated 12 percent of the state's doctor visits were for flu-like symptoms. ( Melissa Phillip / Houston Chronicle )

Companies that provide on-site flu shots typically do so during the fall. By Thanksgiving, employees are no longer rolling up their sleeves in the corporate conference room.

Not this flu season. During the past week, TotalWellness, which provides vaccinations, screenings and other health services for companies nationwide, has received a flood of calls asking if there's time to squeeze in a round.

Lisa Stovall, a spokeswoman for the Omaha, Neb.-based company, said this year's flu outbreak has led some schools around the country to close and has many employers looking at empty desks.

TotalWellness, with more than 3,000 nurses around the U.S., including Houston, has been dispatching them to companies in need.

Employers looking for last-minute shots also are motivated by the potentially high health care costs they face from employees who get sick from the flu, Stovall said, noting that the benefits of a healthy workforce can more than make up for the cost of at-the-office vaccines.

TotalWellness has an online return-on-investment calculator that helps managers make the financial case that corporately subsidized flu shots will save money in the long run, said Stovall, who estimates that 10 to 20 percent of employees are absent at work at some point during a typical flu season.

Many large companies already know the value of on-site flu shots.

In The Woodlands, Anadarko Petroleum Corp. has an extensive, and popular, corporate wellness program that includes an on-site physician and clinic.